The liberation of tissue-damaging enzymes from PMNs may be a determinant factor in the pathogenesis of periodontal disease. The applicants propose to study the PMN release reaction induced by representative oral microorganisms. We will incubate human and rabbit PMNs with bacteria isolated from dental plaques and determine which micro-organisms are capable of triggering the release of a battery of acid hydrolases including C3 and C5 cleaving enzymes from PMNs. In order to determine the mechanism of PMN-parasite interaction we will monitor PMN phagocytic activity, PMN viability and PMN degranulation (assessed by electron microscopy) and the adherence of microorganisms to the cells. We will determine whether immune sera and complement modify these phenomena, and we will ascertain whether certain microbial components are capable of triggering or modifying PMN release. We also propose to see if oral microorganisms which are incapable of inducing PMN release can modify the response produced by "active" organisms. A series of studies will be instituted to compare the PMN release inducing potentials of supra and subgingival human plaque and of plaque obtained at varying intervals after accumulation on the surfaces of teeth. Further, we intend to compare the magnitude of the PMN release response triggered by specific oral bacteria incubated with PMNs collected from several individuals. If variations in the intensity of the response of individual cells are observed, we will ascertain if this correlates with the clinical severity of gingival inflammation produced by the cessation of oral hygiene procedures. We believe that these experiments are relevant to a better definition of the mechanisms and potential consequences of PMN-parasite interaction in the development of periodontal disease.